1. Field of the Invention
The present invention concerns the printing industry and more particularly web folding machines. One of the steps of folding a printed web is to temporarily grip the web and then release that gripping. In order to make accurate folds it is necessary to uniformly grip a printed web over its full width. The instant invention employs a gripper with a fixed or stationary jaw and a movable jaw. The invention directly relates to the accurate movement of the movable jaw toward and away from the fixed jaw to uniformly grip a bight of a printed web.
2. Description of the Prior Art
In our two earlier U.S. patents we employed grippers for engaging a printed web in its folding. In both of these prior patents, a rod, identified by the numeral 40 in U.S. Pat. No. 4,073,485 and by the numeral 45 in U.S. Pat. No. 4,113,243, was used to effect an opening and a closing of the movable jaw of the gripper. The rods 40 and 45 were mounted in such a manner as to permit rocking. The movable jaw was joined with one side of the rod and a depending arm from the other substantially diametrically opposite side of the rod was provided with actuating arms at each end. These actuating arms were caused to be arcuately swung by cams in the end of the web folding machine. Thus, as the cams engaged the actuating arms the rod was rotated a sufficient degree to either close or open the gripper means.
The folding machines are used to effect a folding of a wide printed web and it is essential that the gripper means used in the folding machine uniformly grip the web over its full width so that accurate folding may be obtained. Both rods 40 and 45 of these previous devices were subject to torque and twisting which adversely affected the uniformity of the gripping of the web and thus it was essential that the diameter of that gripper actuating rod be increased substantially to hold the desired uniformity of gripping. Now with the advent of even greater widths of printed webs being folded the required diameter of the actuating rod in our previous devices becomes prohibitive because of weight and size.
The present invention concerns the uniform gripping of a wide printed web over its full width without the employment of a rod which is subject to torque and twisting.